Food Frequency Questionnaires

Food Frequency Questionnaires (FFQs) are flexible instruments for collecting dietary information. FFQs are commonly used in nutritional and medical studies. They always include a list of foods and a range of frequencies that respondents can select from for each food; they sometimes also include options for serving sizes. They are our preferred instrument for assessing dietary change when this must be done through self-reported data.

We recommend especially the two formats given below and on the complete list of recommended questions. The first version does not strongly indicate a specific interest in animal products and thus is useful, with or without the columns for serving size, when the purpose of the survey is not intended to be clear to the respondent. Including the columns for serving size allows more detailed calculations regarding total consumption to be made. The second version is shorter, but gives more information about the purpose of the survey, which could increase bias in responses.

Instructions for modifying these questions and calculating consumption based on responses are given below the examples.

Examples

Thinking about your diet over the past three months, please select the responses that best describe how often you eat each type of food and how much of it you eat at a time. Select only one frequency and one serving size per row, even if different responses have been correct for different days or weeks.

Thinking about your diet over the past three months, please select the responses that best describe how often you eat each type of food. Select only one response per row, even if different responses have been correct for different days or weeks.

Modifications

FFQs are flexible instruments that can easily be modified to address past or future diet. They can also be adjusted to be shorter and easier to complete or longer and more informative. Below, we suggest modifications that allow for customization while retaining the possibility of cross-comparison across studies using different FFQs.

Time Period

Both of the examples above address diet in the past three months. This time period was chosen to give a view of respondent’s present diet, with three months a long enough time period that brief and temporary changes (such as a vacation or illness) would not be likely to substantially alter responses. A survey given fewer than three months after an intervention intended to change diet should use a shorter time period, so that the time period in question does not overlap the time of the intervention. (In fact, some gap between the time of the intervention and the time period specified in the question would increase the probability that participants are responding strictly based on their diet after the intervention.)

FFQs can be modified to ask about past diet by specifying time periods that are in the past. It is helpful to use specific dates in this case, so that respondents do not have to do mental calculation. For instance, “from January 1 to March 31, 2013” is more useful than “9 months to 1 year ago”. To address diet change, identical FFQs could be administered at two different times so that the periods they asked about did not overlap, or two FFQs could be administered on the same survey, one asking about the past and one asking about the present.

FFQs could also address future or planned diet by using dates in the future, but note that people are not generally very reliable sources of information about their future habits. (For instance, people are much more likely to claim they will vote in an upcoming election than to vote in it, and we all have personal experience with times when we or others around us have not followed through on plans.) Measurements of respondents’ intentions with regard to dietary changes can provide interesting information about the persuasiveness of a message, but are not as telling as measurements of actual dietary change.

Food List

The examples above use two similar food lists. The choice of food list plays a significant role in the information available from an FFQ, and many factors should be considered, including:

Length To increase response rates and quality, use the shortest list that meets the needs of the survey. All the lists we provide are short compared to lists used in nutritional and medical studies, which can contain hundreds of individual foods.

Balance of animal products and plant-based foods Survey responses can be affected by the perceived purpose of the survey. Choosing a list that asks many more questions about animal products than about plant-based foods can indicate to the respondents what aspect of their diet the researchers find interesting, so a balanced list is preferable if respondents will not already know who is surveying them (and why) and would think an animal advocacy group may be responsible for the survey. Similarly, including other categories of food that have social or medical significance, like caffeinated beverages, may provide respondents with alternative possibilities to consider about the purpose of the survey, leading to less biased answers on questions about animal products.

Specificity of animal products listed Not all animal products are equally important to ask about specifically. Products which are consumed more frequently and which lead to greater suffering are more important to ask about than products which are consumed infrequently or lead to less suffering. Accordingly, our lists place great emphasis on chicken consumption, since it is frequent and leads to the suffering of more individuals per serving than do many other animal products. We place less emphasis on infrequently consumed species such as rabbit, combining them into a single category (i.e., other meat). Our longest list also separates cheese from the rest of the dairy category, since in the United States, more milk is used to produce cheese than to produce any other dairy food.

Cultural relevance Our lists, including the memory aids, were developed with a broadly typical US diet in mind. We selected foods for their prevalence in the United States, both in generating the list of categories and in choosing specific examples to use as memory aids. In adapting an FFQ for use in another country or with a US population for which the foods listed are not especially common, culturally appropriate foods should be used to replace those not thought to be consumed frequently by the target population.

Order of items Respondents are most likely to answer questions accurately after they have become used to the format of the questionnaire, but before they have become bored. Items to which a correct response is particularly important should be placed near but not at the beginning of the list.

We provide three food lists with memory aids, including the two used above and a longer list which would be more useful for producing precise calculations of the quantity of various animal products consumed.

To aid respondents, if more than one FFQ is present on a survey, each should use the same food list if possible.

Comprehensive

Description: This list includes many subcategories of animal derived foods. The larger number of categories should help respondents more thoroughly recall their consumption habits. Additionally, separate categories for side and main dishes help in assigning accurate portion sizes and calculating the number of animals affected. However, the large number of items focused on animal derived foods might reveal the purpose of the study if it is not already clear to respondents.

When to use this list: Use this list when precise calculation of the number of animals impacted is required and when survey length is not a concern. If respondents should not know the purpose of the survey, consider supplementing with additional items focused on health or marketing issues. For instance, include a series of items addressing consumption of caffeine (coffee, tea, caffeinated soft drinks, energy drinks, and chocolate).

Balanced

Description: This list includes an equal number of questions about animal-derived and plant-derived foods. Its presence on a survey will not be a strong clue to respondents that the goal of the study is to determine their attitudes toward animals or whether they eat animal products. Enough categories of animal products are provided to avoid some basic definitional confusions (such as the notion that fish and chicken are not meat), but recall will likely be less thorough than with the comprehensive list.

When to use this list: Use this list when respondents should not know the purpose of the survey and when precision in terms of serving sizes is not required.

Food

Memory Aid

Fruit

apples, bananas, oranges, etc.

Vegetables

carrots, mushrooms, potatoes, etc.

Chicken

fried chicken, in soup, grilled chicken, etc.

Turkey

turkey dinner, turkey sandwich, in soup, etc.

Fish and Seafood

tuna, shrimp, crab, etc.

Pork

ham, pork chops, ribs, etc.

Beef

steak, meatballs, in tacos, etc.

Other Meat

duck, lamb, venison, etc.

Nuts

almonds, cashews, walnuts, etc.

Beans

tofu, chickpeas, chili, etc.

Dairy

cheese, milk, yogurt, etc.

Eggs

omelet, in salad, in baked goods, etc.

Grains

breads, pasta, rice, etc.

Sweets

candy, cookies, pie, etc.

Caffeinated Soft Drinks

cola, diet cola, energy drinks, etc.

Coffee and Tea

hot coffee, iced coffee, black tea, etc.

Short

Description: This list includes only the items about animal products from the balanced list. Because it is very short, it is quicker and easier to administer than the other lists. Enough categories are provided to avoid problems caused by basic definitional confusions (such as the idea that chicken is not meat). However, this list is likely to reveal the purpose of the study to respondents if they do not already know it. It also provides less support for memory than the comprehensive list, so recall is likely to be less thorough.

When to use this list: Use this list when the other options are inappropriate because respondents will not have time or attention to complete them.

Food

Memory Aid

Dairy

cheese, milk, yogurt, etc.

Chicken

fried chicken, in soup, grilled chicken, etc.

Turkey

turkey dinner, turkey sandwich, in soup, etc.

Fish and Seafood

tuna, shrimp, crab, etc.

Pork

ham, pork chops, ribs, etc.

Beef

steak, meatballs, in tacos, etc.

Other Meat

duck, lamb, venison, etc.

Eggs

omelet, in salad, baked goods, etc.

Frequency Scale

The frequency scale used should be chosen by balancing the precision of the information obtained with the increased difficulty for respondents when more response categories are available. We provide three scales, including the two used in the examples above. All scales focus attention on relatively frequent consumption over relatively rare consumption, both because the categories given on our food lists tend to be broad and because gradations on the frequent end of consumption possibilities affect more animals than gradations on the infrequent end. However, we always include “never” as a possible response, because of its significance in terms of respondent memory and to allow those administering a FFQ to identify respondents who are following a vegan or vegetarian diet. These scales are compatible with each other, in that scales with fewer options can be obtained by combining categories on scales with more options.

To aid respondents, if more than one FFQ is present on a survey, each should use the same frequency scale if possible.

9-point scale

never

less than 1 time per month

1–3 times per month

1-3 times per week

4–6 times per week

1 time per day

2 times per day

3 times per day

4 or more times per day

7-point scale

never

less than 1 time per week

1-3 times per week

4-6 times per week

1 time per day

2-3 times per day

4 or more times per day

5-point scale

never

less than 1 time per week

1-6 times per week

1-3 times per day

4 or more times per day

Serving Size Scale

The inclusion of a serving size scale is optional, but allows for more precise calculation of the number of animals affected by a respondent’s diet. If serving sizes are included, they can be included parallel with the frequency scale, as in the first example above, or in a separate question following the other part of the FFQ. Serving sizes may be given in words, as in the examples we present, or with pictures, especially if the survey is administered on a computer. Because most people find serving sizes difficult to estimate from verbal descriptions, pictures may produce more accurate responses.

Use the items from the serving size list below that correspond to the food list on the survey. If adjustments are necessary to make the food list and memory aids culturally appropriate, they should also be considered for the example serving sizes given. If the serving size questions are presented separately from the frequency questions, keep the food list in the order used for the frequency questions.

For broad categories, an effort has been made to make serving sizes of different items in the category roughly interchangeable, in terms of the amount of animal product used.

Standard serving size

1

1/2 or less

1 1/2 or more

Fruit

½ cup raw fruit; ½ medium apple or large orange

Vegetables

½ cup cooked or raw; 1 carrot or stalk celery

Soft Drinks

1 can; 12 oz

Cheese

2 oz; 3 slices cheese; 1 slice pizza

Dairy main

1 cup milk; 1 cup yogurt; 1 ½ cups ice cream

Dairy side

1 tbsp butter or sour cream; 1 packet of creamer

Dairy other

1 cup goat’s milk; 2 oz goat or sheep cheese

Chicken main

3-4 oz; ½ large or 1 small breast; 2 drumsticks

Chicken side

1 cup soup; ½ cup chicken salad; 2 tbsp gravy

Turkey main

3-4 oz; 6-8 very thin slices; 1-3 thick slices

Turkey side

2 tbsp gravy; 1 cup soup

Fish (not shellfish)

3-4 oz; 1 can of tuna; 1 small or ½ medium fillet

Shellfish

3-4 oz; 6 medium shrimp; 6-12 oysters

Pork main

3-4 oz; 1 pork chop; 2 ribs; 3-4 slices bacon

Pork side

1 piece pepperoni pizza; 1 cup pork fried rice

Beef main

3-4 oz; ¼ lb burger; 3-6 slices roast beef

Beef side

2 tbsp gravy; 1 meatball; 1 oz beef jerky

Other beef/pork

3-4 oz; 1-2 hot dogs; 4 breakfast links

Other meats

3-4 oz; a piece about the size of your palm

Eggs main

1 egg; ⅓ cup scrambled eggs or egg salad

Eggs side

2 tbsp dressing; 1 cup egg noodles; 1 slice cake

Nuts

⅓ cup or 1 handful; 20 almonds; 2 tbsp nut butter

Beans

½ cup cooked beans; ¼ cup hummus or tofu

Grains

1 slice bread or pizza; ½ cup rice or pasta

Dairy

3 slices cheese; 1 cup milk; 1 cup yogurt

Eggs

1 egg; ⅓ cup scrambled eggs or egg salad

Chicken

3-4 oz; ½ large or 1 small breast; 2 drumsticks

Turkey

3-4 oz; 6-8 very thin slices; 1-3 thick slices

Fish and seafood

3-4 oz; 1 can of tuna; 6 medium shrimp

Pork

3-4 oz; 1 pork chop; 2 ribs; 3-4 slices bacon

Beef

3-4 oz; ¼ lb burger; 3-6 slices roast beef

Other meat

3-4 oz; a piece about the size of your palm

Sweets

2 small cookies; 1 slice cake or pie

Caffeinated soft drinks

1 can (12 oz) soda; small fountain drink

Coffee and tea

6 oz. hot coffee or tea; small iced coffee

Calculations

A food frequency questionnaire can be used without significant calculation, if it is only intended to determine whether respondents eat a certain type of food at all, although in this case it may simply be better to use the food list with a question such as “Which do you currently eat?” to reduce the burden on respondents. If a measure of overall consumption levels is required, calculation will be necessary.

Without Serving Sizes

If no serving size scale was included, the best justified calculation that can be made is the frequency of consumption. Ranges on the frequency scale can be converted into frequencies of consumption per day and averaged over the relevant group of respondents.

Our suggested daily frequencies for the categories on the frequency scales given above follow:

9-point scale

never

less than 1 time per month

1–3 times per month

1-3 times per week

4–6 times per week

1 time per day

2 times per day

3 times per day

4 or more times per day

Daily Frequency

0

0.02

0.07

0.29

0.71

1

2

3

4.5

7-point scale

never

less than 1 time per week

1-3 times per week

4-6 times per week

1 time per day

2-3 times per day

4 or more times per day

Daily Frequency

0

0.07

0.29

0.71

1

2.5

4.5

5-point scale

never

less than 1 time per week

1-6 times per week

1-3 times per day

4 or more times per day

Daily Frequency

0

0.07

0.5

2

4.5

Using these conversions, the first step is to process the data by converting each response into a daily frequency.

If the sample consisted of only these two respondents, the overall average daily frequencies could be computed as in the chart below. With more respondents, all daily frequencies would be averaged. Non-responses would be left out entirely, and the average taken over respondents who provided a response to the particular question.

Food

Respondent 1

Respondent 2

Sum

Average = (Sum / Number of Respondents)

Dairy

2

4.5

6.5

3.25

Chicken

0.5

0.07

0.57

0.285

Turkey

0.5

0.07

0.57

0.285

Fish and Seafood

0.07

0.07

0.14

0.07

Pork

0.07

0.07

0.14

0.07

Beef

0.5

0.07

0.57

0.285

Other Meat

0

0.07

0.07

0.035

Eggs

2

0.5

2.5

1.25

We do not recommend the reduction be calculated by counting the number of respondents who “moved to the left” on the scale, as if each step to the left is equally significant. While any reduction in animal product consumption is beneficial to animals, each step to the left on frequency scales is not equally significant with each other step to the left. In the example above, a move from the rightmost column to the next column over would represent about 60 fewer servings of a food type per month, whereas the next step over would only represent a further decrease of about 45 servings per month, and each successive step after that also represents fewer servings’ difference.

If respondents are administered the same FFQ at different times, or if the survey contains two FFQs referring to different time periods, the change in consumption for each individual respondent can also be calculated. For instance, suppose the two responses above were given by the same respondent before and after a humane education program.

Food

Before Program

After Program

Change = (After – Before)

Dairy

2

4.5

2.5

Chicken

0.5

0.07

-0.43

Turkey

0.5

0.07

-0.43

Fish and Seafood

0.07

0.07

0

Pork

0.07

0.07

0

Beef

0.5

0.07

-0.43

Other Meat

0

0.07

0.07

Eggs

2

0.5

-1.5

Respondents can then be classified by the amount of change in their diet over the period of interest.

With Serving Sizes

Including serving sizes allows an informed conversion to be made from daily frequency to ounces consumed daily, and from there to the number of animals affected. The first step in calculating the number of animals affected, therefore, is to compute the daily frequency for each respondent, as above. The daily amount (measured in servings) is this frequency, multiplied by a factor of 1, 0.5, or 1.5, depending on the serving size selected. If no selection is made for serving size, the response may be omitted, or the serving size may be taken to be 1; a choice should be made systematically for the entire data set.

Once daily amounts are obtained for all respondents in the group, they may be averaged to produce an average daily amount. If respondents are administered the same FFQ about two different periods, change in amount eaten per day for each respondent could also be calculated, by the method used about for change in frequency.

Food

Respondent 1

Respondent 2

Sum

Average = (Sum / Number of Respondents)

Dairy

2

2.5

4.5

2.25

Chicken

0.5

0.07

0.57

0.285

Turkey

0.25

0.07

0.32

0.16

Fish and Seafood

0.11

0.07

0.18

0.09

Pork

0.04

0.07

0.11

0.055

Beef

0.25

0.11

0.36

0.18

Other Meat

0

0.04

0.04

0.02

Eggs

2

0.75

2.75

1.375

Average daily amounts can then be used to calculate numbers of animals affected per person per year, based on the standard serving sizes used. For instance, in the example above, 2.25 servings of dairy per day is about 18 oz of milk per day, or 411 lbs per year, which is about 2% of one dairy cow’s annual production. Similarly, .285 servings of chicken per day is about 1 oz of chicken per day, or 23 lbs per year, which is the meat from about 8 chickens. These calculations must be done separately for each category of animal product.

If serving size information is not solicited, conversions to animals affected may be made by assuming all respondents are using typical portion sizes, but there is a lack of data on what these sizes are, particularly for the broad categories of foods on our food lists, so this is expected to introduce significant potential for error into calculations.

Conclusion

We hope this page has given you the tools you need to select and use a food frequency questionnaire for your survey. We encourage you to use the example questionnaires above or to modify them by choosing the food list, memory aids, and frequency scale that best suit your needs. Any questionnaire can be used with or without serving size information. If you have further questions about what questionnaire would be right for your purposes, or about how to modify a questionnaire for a substantially different audience, you can contact Faunalytics or get help through Statistics Without Borders.